Over the last few years adjustable bent housings have become well known in the oil industry in connection with the use of downhole drilling motors. For downhole drilling a number of components are used in conjunction with the downhole drilling motor. These components are a drill bit, a bearing assembly, a drive shaft, and a housing in which the drive shaft is housed. The downhole drilling motor produces an eccentric motion. The bearing assembly absorbs the radial and thrust loading from the drill bit and drives the drill bit in a concentric motion. The drive shaft is constructed with a universal joint type of connection to convert the eccentric motion of the drilling motor into concentric motion required by the bearing assembly. The drive shaft passes through the housing which is secured at one end to the drilling motor and at the other end to the bearing assembly.
In directional drilling a bend is placed in the drill string in order to cause the borehole created by the drilling process to deviate at an angle from the vertical. It is desirable to get this "bend" as close as possible to the drill bit, this is accomplished by using a bent housing. It is, however, inconvenient to disassemble the bearing assembly, drive shaft, and drilling motor in order to replace the bent housing with a different bent housing with a bend of a different magnitude. For this reason adjustable bent housings were developed. The magnitude of the bend in an adjustable bent housing is adjustable by relative rotation of two mating components. The current state of the art is reflected in U.S. Pat. No. 4,813,497 which issued to Kenneth H. Wenzel.
As the art of directional drilling progresses, the practice has developed of using an adjustable bent sub, in combination with another bent sub positioned above the drilling motor. Using two bent subs in this manner allows the borehole to be drilled at an greater angle in less time than would be possible when using only one bent sub. A problem has arisen, however, in getting the bends in the two bent subs to align. A separate tool has been developed which addresses this problem which is referred to as an orientation sub. The use of an orientation sub adds one more component to the drilling motor assembly which is viewed as undesirable.